"Joaquin, I'm sorry you couldn't be here tonight." David Letterman

As a piece of performance art, I'm Still Here is as good a mockumentary about celebrity insanity as you will ever get, except, of course, for This is Spinal Tap, which is the real deal of satire. Director Casey Affleck follows his brother-in-law for more than a year after Phoenix's decision to retire from his successful acting career and become a hip-hop artist.

The iconic, Nick-Nolte-like image of Phoenix with a beard and sunglasses, a sort of Blues Brother and Smith Brother all in one, is both hilarious and sad, depending on whether you believe the story of his retirement or see it as a smart marketing campaign for this film and his career. His expertly scoring blow and constantly smoking weed have an authentic air about them although a good actor could simulate. His abuse of his many paid assistants is accurate for a star but almost unbelievable for such a talented one (Walk the Line, Revolution Road). The poor quality of the sound and image makes it a Blair-Witch kin or a device to evoke realism.

I am a disbeliever because although Phoenix convinces me he is sincere about retirement, the actual lack of talent he has, evidenced more than once in the film, leads me to think it's a finely-wrought hoax. No actor as smart as Phoenix could ever judge himself talented, especially as he forms a relationship with Sean Combs, one of the great rappers of our time and in the film a shrewd judge of Phoenix's sophomoric attempts. Phoenix's gig with Letterman, see quote at beginning, could have been a part of the hoax. Throwing up after a performance looked real enough.

Phoenix could make himself into a minor rap artist if he wanted—witness his successful learning to play guitar and sing as Johnny Cash—yet it seems he prefers not to learn well just so he can fail and return into acting, where the dollars will follow.

The title is instructive—does it mean the acting Phoenix is still here, or does it suggest his whole persona—musician and actor—is here. I don't know the answer; I just know my film critic side thinks it sees a con.

If it is all true, Joaquin Phoenix will have time to get back to his real talent, acting. If not, he'll spend time mending a reputation he has willfully wrecked.